修复考试工坊试卷历史记录问题

shudao-vue-frontend/src/views/ExamWorkshop.vue

@@ -3043,7 +3043,7 @@ const restoreExamFromHistory = (examData) => {
           questions: singleChoice.questions.map(q => ({
             text: q.text || q.question_text,
             options: q.options || [],
-            selectedAnswer: q.selectedAnswer || ""
+            selectedAnswer: q.selectedAnswer || q.correct_answer || q.answer || ""
           }))
         },
         judge: {